1. Field of the Invention
The present invention relates to a method of correcting the wheel unbalance of a vehicle and to a wheel unbalance detecting device.
2. Description of the Prior Art
When a wheel of a vehicle is unbalanced, it is known that vibrations occur in the vertical, longitudinal and lateral directions during rotation of the wheel. (The lateral direction herein refers to the steering or vehicle side direction)
Generally, the vertical and longitudinal vibrations are considered to result from a circumferential weight unbalance (static unbalance) of the wheel. The lateral vibration is considered to be caused by a lateral weight unbalance (dynamic unbalance) of the wheel. The inventor of this invention previously proposed, in the Japanese Patent Application No. 142627/1985, a wheel unbalance correction method wherein a wheel attached to a vehicle body via a suspension mechanism is placed and rotated on a rotating drum to detect the three amplitudes in the vertical, longitudinal and lateral directions of an unsprung member of the wheel suspension mechanism other than the wheel itself. The amount of the static unbalance is then determined from the vertical and longitudinal amplitudes and the amount of the dynamic unbalance from the lateral amplitude. Weights corresponding to these amounts of the unbalances are attached to the respective unbalance points on the rim of the wheel for correction of the wheel unbalances.
Even with the above method, however, the wheel unbalance cannot always be corrected as desired and there are instances where a wheel unbalance correction has to be repeated.
The analysis conducted by this inventor has revealed the cause of the above problem is that the vertical vibration of the unsprung member is affected by the suspension function of the suspension mechanism and by the uniformity of the tire, indicating that there is no unitary relationship between the vertical amplitude and the static wheel unbalance. Likewise, the lateral vibration is affected by the vertical and longitudinal vibrations of the wheel, resulting from the static wheel unbalance. Further, the lateral vibration is affected through a gyroscopic action resulting from the vertical and longitudinal vibrations, and also by the compliance in the lateral direction of the suspension mechanism, again indicating that there is no unitary relationship between the lateral amplitude and the dynamic wheel unbalance. The problem, therefore, comes from the fact that a weight is selected on the basis of these unrealistic amplitudes.